Formation mechanism of zeolite-templated carbons
Formation mechanism of zeolite-templated carbons
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DOI：
10.7209/tanso.2017.169
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发表时间：
2017-11
期刊：
影响因子：
10.9
通讯作者：
H. Nishihara;Katsuaki Imai;Hiroyuki Itoi;K. Nomura;K. Takai;T. Kyotani
中科院分区：
文献类型：
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作者：
H. Nishihara;Katsuaki Imai;Hiroyuki Itoi;K. Nomura;K. Takai;T. Kyotani
研究了沸石模板碳(ZTC)的形成机理。在化学气相沉积(CVD)过程中，分子筛纳米通道的吸碳过程经历了以下三个阶段：(1)从沸石颗粒表面向中心快速吸碳，(2)碳密度以恒定速率逐渐增加，(3)碳沉积终止。并对分子水平的结构演化进行了详细分析。通过化学气相沉积，在沸石的纳米通道内形成了弯曲的纳米管，但它们之间并不是完全相连的。随后的热处理(>；800°C)将纳米管结合成连续的3D骨架，同时形成大量的悬挂键(未终止的边缘位置)，这些键被沸石保护不受空气影响，因此它们在室温下是稳定的。然而，在去除模板时，悬挂键与环境中的H2O或O2反应，并被氧官能团或H终止。当在700℃下对碳/沸石复合材料进行氢气处理时，碳/沸石复合材料中的悬垂键也可以被H终止。在这种情况下，碳/沸石复合材料中的悬垂键的数量减少，并且当模板被移除时，氧官能团的增加变得不那么显著。
The formation mechanism of zeolite-templated carbons (ZTCs) is investigated. The carbon uptake into zeolite nanochannels during chemical vapor deposition (CVD) is found to proceed in the following three stages: (i) initial rapid carbon uptake from zeolite-particle surface to its center, (ii) gradual increase of carbon density at a constant rate, and (iii) termination of carbon deposition. The molecular-level structure evolution is also analyzed in detail. By CVD, curved nanographenes are formed inside the nanochannels of zeolite, and they are not perfectly connected each other. The subsequent heat treatment (>800 °C) coalesces the nanographenes to form a continuous 3D framework, and at the same time, a significant number of dangling bonds (non-terminated edge sites) are formed that are protected from air by the zeolite so that they are stable at room temperature. However on template removal, the dangling bonds react with ambient H2O or O2 and are terminated by oxygen-functional groups or H. The dangling bonds in the carbon/zeolite composite can also be terminated by H when the composite is subjected to a H2 treatment at 700 °C. In this case, the number of dangling bonds in the carbon/zeolite composite is decreased, and the addition of oxygen-functional groups when the template is removed becomes less significant.